The problem of separating or removing contaminants from aqueous systems has been a complication that the art has lamented over for many decades. To this end, the art developed along with further industrial processes as water contamination grew commensurately with industrial progress. Initially, water treatment was simply a matter of adding materials suitable for inducing precipitation of certain materials, filtration, ion exchange and other processes. With the continual increase in strict requirements for clean water, electro chemistry was brought into favor. Broadly, the use of electrodes disposed within a cell and subjected to electric current was found to be useful for treating solutions containing contaminants. In some instances, other unit operations were combined with this treatment process in order to render inert compounds.
One of the references that was selected for review is U.S. Pat. No. 1,095,893, issued to Landreth, May 5, 1914. This patent relates to electrochemical treatment and in this patent, the patentee has identified that such cells are useful for the treatment of water. As stated in the disclosure electrodes of copper, aluminum, brass or other alloys are useful as cell plate material. In addition, the disclosure discusses the fact that settling tanks may be useful to assist in material settling (floccing). Column 2 of the disclosure indicates that the series of electrodes are arranged so that the water passes up through the apparatus and is forced to " . . . to take a circuitous course whereby any material added to it or found in it may be thoroughly mixed and all particles of the liquid be brought into contact with the electrodes . . . ". It is also as stated in the text at column 2, that the electrodes are in the form of horizontally disposed plates and that the plates may be provided with apertures which may be centrally arranged with the plates of alternating series of other plates have recesses at their ends. Column 3 of the disclosure states:
"To provide for the proper passage or circulation of the liquid between plates 14 and its movement throughout the apparatus, alternate plates are provided with apertures indicated at 14A, while the intermediate plates have their cut-away corners notched or recessed as at 14B as clearly illustrated in FIGS. 8 and 9. By this means, the liquid under treatment is diverted in its flow and caused to contact with the entire surface of the respective plates, insuring the desired electrical treatment." PA1 providing an aqueous solution containing contaminants; PA1 providing a closed reservoir having an inlet and an outlet, the inlet at a higher elevation than the outlet; PA1 introducing the aqueous solution into the reservoir; PA1 entraining an oxidant into the aqueous solution; PA1 maintaining super atmospheric pressure in the reservoir to minimize bubble size of the oxidant to thereby maximize available surface area of bubbles of oxidant with the contaminants in the aqueous solution; PA1 oxidizing the contaminants; and PA1 selectively inducing a pressure discontinuity extraneous of the reservoir to flocculate oxidized contaminants into a separate phase from the aqueous solution. PA1 providing an aqueous solution containing contaminants; PA1 providing a closed reservoir having an inlet and an outlet, the inlet at a higher elevation than the outlet; PA1 positioning an electrocell with the reservoir for applying an electric field to the aqueous solution; PA1 introducing the aqueous solution into the reservoir; PA1 entraining an oxidant into the aqueous solution; PA1 maintaining super atmospheric pressure in the reservoir to minimize bubble size of the oxidant to thereby maximize available surface area of bubbles of oxidant with the contaminants in the aqueous solution; PA1 oxidizing the contaminants and the oxidant and flocculating the contaminants by exposure to the electric field; and PA1 selectively inducing a pressure discontinuity extraneous of the reservoir to flocculate any remaining oxidized contaminants into a separate phase from the aqueous solution. PA1 a. providing an aqueous solution containing contaminants; PA1 b. oxidizing the aqueous solution with an oxidant under adjustable super atmospheric pressure to maintain the oxidant in solution; PA1 c. exposing the aqueous solution to an electrocell for electrocoagulating contaminants; and PA1 d. selectively inducing a pressure discontinuity to flocculate coagulated and oxidized contaminants into a separate phase from the aqueous solution. PA1 an aqueous source containing contaminants; PA1 a closed pressurizable reservoir having an inlet and an outlet, the inlet being disposed at a higher elevation than the outlet, the inlet in communication with the aqueous source; PA1 means for introducing an oxidant under pressure into the reservoir; PA1 an electrocell disposed within the reservoir for electrocoagulating material in the aqueous source; PA1 means for supplying current to the electrocell; and PA1 means for selectively inducing hydrodynamic cavitation in treated aqueous solution to flocculate oxidized contaminants into a separate phase from the aqueous solution.
Although this disclosure is useful for instructing the procedure for electrochemical treatment of water, there is no indication of the addition of an oxidant material such as ozone. Further, the teachings of this patent are limited to electrochemistry; the disclosure fails to set forth any details with respect to dissolved air flotation, fluid hydrodynamics, cavitation, flocculation or any other fluid dynamic principles that would augment the utility of the electrochemical cell taught in this patent.
In U.S. Pat. No. 1,146,942, issued to Landreth, Jul. 20, 1915, a variation on what has been discussed in the previous patent is set forth. In this reference, there is a clear indication that the electrodes are of a different polarity and that a suitable pole changing switch, an example is given as number 26 in the drawings, could be used to switch the current in order that one set of plates act as cathodes for a certain length of time while another set of plates act as anodes during this period of time. This reference advanced the art by providing a reverse polarity arrangement for changing the polarity of the individual cells within the unit. The reference, similar to its companion, is deficient on appreciation of countercurrent oxidation with a dissolved gas. Further, it is believed that this apparatus would not be particularly well suited to handling a wide variety of contaminant types (organic, inorganic, combinations thereof, etc.)
In a further reference issued to Landreth, namely U.S. Pat. No. 1,131,067, issued Mar. 9, 1915, there is a discussion of reintroducing treated liquid for further treatment by the apparatus as well as a discussion concerning oxidizing treatment or a treatment for the production of flocculent formed either from the metal electrodes or from simple chemical reaction or the latter stimulated by electric current; or any other treatment. At column 2, beginning at line 25 et seq., discusses recirculation of the material for further treatment in the apparatus.
Preis et al., in U.S. Pat. No. 3,728,245, issued Apr. 17, 1973, teach an apparatus for treating sewage incorporating a series of electrolytic plates for the purpose of electrocoagulation. The patentees discuss a need for maintaining pressure in the circuit so that chlorine and ozone are maintained in solution in order to enhance bactericidal action. This reference advanced the art developed by Landreth et al., by employing an oxidant to enhance the electrocoagulation. The reference, although providing further instruction in this art, is deficient any discussion cavitation or floc generation by pressure discontinuities in an outlet stream of treated aqueous material.
Other generally relevant references include U.S. Pat. No. 913,827, issued to Korten, Mar. 2, 1909, U.S. Pat. No. 3,523,891, issued to Mehl, Aug. 11, 1970, U.S. Pat. Nos. 5,928,493; 5,705,050; 5,746,904 and 5,549,812, 3,846,300, 5,587,057 and 5,611,907.
The electrolytic processes were found to be generally useful, however, the cellular design was such that the electrodes often would accrue debris and, therefore, would change the requirements of the current of the cell. In addition, many of the plates in the existing arrangements were fairly large and did not provide any improvement to enhance the surface area to therefore increase the number of reactions with the contaminants to be treated in the water. This, of course, leads to lower degree of interactions and a higher cost of running the cell in terms of the current requirements due to debris buildup.
It has also been proposed to employ dissolved air flotation systems. One such arrangement is made by the Precision Environmental Systems Company. This company manufactures devices which are useful for flocculation and coagulation within the same unit. This unit is quite useful for the purpose for which it was designed, however, the arrangement has an extremely large footprint and does not provide for different chemical processes to occur within the same unit.
Of the more desirable arrangements that have evolved in this art for water treatment are perhaps the use of dissolved gases for the purpose of oxidation has been moderately successful. In the art that is currently known, typically oxidation cells are open to atmospheric pressure where a gas dissolved in solution is allowed to evolve out of the solution. The arrangement in the art provide a tortuous path or other applied force in order to keep the bubbles in solution as long as possible. This has the advantage of providing a reaction site (the surface of the bubble) of the oxidant material so that the contaminant can be oxidized. Once the gaseous material then evolves to the surface, the contaminant is flocculated and the materials then separated. This is broadly known as aeration and various devices have been proposed in this art in order to maintain the bubbles in solution and thus enhancing the degree of interaction of the bubble surface with the material to be oxidized or otherwise decontaminated.
It would be desirable if there were a process whereby a gaseous oxidant could be introduced into a reservoir or other chamber or confined area under sufficient pressure to maintain the gas in solution. This affords the opportunity for the smallest possible bubbles in solution to oxidize contaminants present in the solution. It would be particularly desirable if there were a system available where the dissolved oxidant gas could be maintained in solution in order to provide the smallest possible bubbles and therefore the greatest possible degree of surface area for reaction with the contaminants to be separated and further, affording control of the bubble size.
The present invention is directed to providing a mass transfer mechanism and advanced oxidation technologies for the separation of contaminants from an aqueous solution where the oxidant is maintained in solution until such time as it is desirable to allow the pressure to be reduced and the oxidant to come out of solution.